Not sure that i got it right but let me try ...
if u want to use another drive for ur applications and websites because u need extra space or because u want ur sites to be on another drive other than the operating system drive this can be solved in more than one way..
my best idea is to mount any other drive as a directory into the htdocs xampp directory through control panel administrative tools computer management
then disk management u can choose any hard drive u have and right click it then go to change drive letter or path click add then click on Mount into this empty ntfs folder and brouse to htdocs directory ...
this will make this harddrive as a directory inside xamp htdocs directory
if i am not in the right path of ur qustion then
U might want to change the whole xamp directory to be in a directory away from the operating system c:
this can be made manually in the xampp config file but i think it is much better to remove and reinstall xampp again in the directory u want
u can review the basic q.s in the xampp download page such as this
Question 3: Can I move the XAMPP installation?
Yes, but only if you installed it using the ZIP (z-zip) archive method. After moving the XAMPP package, you must execute the "setup-xampp.bat" to update all configuration files. In this case you can make a copy of XAMPP and put this in a directory somewhere. At last execute the "setup-xampp" and make your tests. Try it out.
If you installed with the Installer, then you must completely uninstall XAMPP and reinstall it at the new location. This is the only way to ensure that all changes made to the registry are cleaned up, and updated for the new location.
on this pagehttp://www.apachefriends.org/en/xampp-windows.html